The present invention relates generally to methods and apparatus for insulating between windings of a dynamo-electric machine and more specifically to methods and apparatus for inserting winding end turn phase insulation in a dynamoelectric stator assembly.
As is well known in the art, dynamoelectric machine stator assemblies may often comprise a magnetic core having a bore, axially extending slots and windings which may comprise a plurality of coils formed by multiple turns of a conductor. The multiple winding turns have side turn portions which are disposed within the axially extending slots, and end turn portions which project from the slots and which are disposed about end faces of the core. The conductors employed in forming the plurality of coils are provided with an electrical insulating coating to prevent short circuiting between the turns and each slot is electrically insulated from the core by, for example, a slot liner in order to prevent grounding of the windings to the stator core. Because winding to winding voltage potential can be appreciable, that is, more than line voltage and substantially higher when capacitors are interconnected with the windings, the conductor turns of one winding are often separated or insulated from the conductor turns of another winding by additional insulation. Without any additional insulation, a touching of the turns of one winding with the turns of another winding with such an appreciable voltage potential existence could shorten the life of the conductor insulation and/or cause insulation failure resulting in a short circuit between the windings. This additional insulation may include insulating wedges or slot separators disposed with the slots of the core to separate side turns of one winding from the side turns of another winding. The end turns of different windings may also touch each other, especially when the end turns are subjected to a blocking or pressing operation to obtain a particular end turn silhouette or configuration and thus, this additional insulation may also include end turn phase insulators disposed about the faces of the core and between end turns of the different windings.
End turn phase insulators are generally mounted or disposed on a stator core by a hand operation. When a hand insertion or manual insertion technique is employed, the phase insulators must be individually disposed or mounted, that is, one at a time on the stator core which adds considerable time and expense to the stator assembly fabrication process. Such a manual insertion operation may require three or four operators inserting end turn phase insulators in order to keep pace with automated stages of a stator assembly fabricating operation. Thus, it would be desirable to develop methods and apparatus for disposing end turn insulators on a core which would reduce the time and labor expense, and which could be employed to dispose a plurality of insulators substantially simultaneously.
Another known approach for disposing end turn phase insulation is to dispose the phase insulators essentially simultaneously with the insertion of multiple windings into the stator core. For example, the end turn phase insulators are disposed between two windings while the windings are on coil injection equipment and then subsequently inserted substantially simultaneously with the two windings. However, insertion of end turn insulators with two or more windings may create a problem of bunching together of the windings and the end turn phase insulators and thus, causing either a hangup in the insertion equipment resulting in downtime of the operation or the need for an additional operation wherein the end turns are pried apart to straighten the insulators disposed therebetween.
The difficulty in inserting end turn phase insulators simultaneously with the windings may be increased when the windings are inserted individually, i.e., utilizing multiple passes of the coil injection equipment. It is often desirable to have a maximum slot fill or maximum number of conductor turns within the slots of the core in order to maximize motor efficiency and material utilization. In obtaining maximum slot fill, it is often desirable to insert each winding individually with an intermediate distributing operation being used between insertion operations of different windings to distribute turns of a previously inserted winding within particular areas of the slots being occupied by the winding. Such individual winding insertion and intermediate distributing techniques tend to minimize forces required for winding insertion into the core and thus, eliminate problems of winding damage which may occur with elevated injection forces. However, individual winding insertion can create problems of inserting or disposing end turn insulators. The insulators can no longer be disposed between two windings for insertion, but rather must either trail the first to be inserted winding or lead the second to be inserted winding. If the end turn insulator is disposed on coil injection equipment so as to trail the first to be inserted winding, the insulator may be damaged by the stripper of the injection equipment as it strips the coils of the winding from the injection equipment to move them into selected slots of the core. On the other hand, inserting the end turn insulator with the second to be inserting winding requires that the insulator lead the second winding during the insertion process. When the insulator leads the second winding, the insulator no longer has winding turns to cushion it against surfaces of the core teeth and thus, may be damaged by sharp edges or protrusions along the surfaces.
Therefore, it would be desirable to develop end turn phase insulator inserting techniques which would minimize the disposing time and labor involved over the individualized hand insertion techniques and techniques which would minimize end turn disposing problems incurred when windings are individually inserted into a core. It would also be desirable to develop end turn phase insulator disposing techniques which would be independent of the winding insertion operations and thus, alleviating any problems of coil injection equipment downtime and the scrapping of winding materials resulting from injection equipment hang-ups.
Accordingly, one of the general objects of the present invention is to develop new and improved methods and apparatus for inserting end turn phase insulators into a dynamoelectric machine stator core.
A more specific object of the present invention is to develop methods and apparatus for simultaneously inserting a plurality of end turn insulators into a stator core.
Another object of the present invention is to develop new and improved methods of inserting phase insulators while minimizing the time and expense of the inserting operation.
Still another object of the present invention is to develop new and improved methods of inserting end turn phase insulators which are independent of coil injection operations and which can be employed in stator assembly fabrication processes requiring individualized insertion of windings.
Yet another object is to develop new and improved methods and apparatus for manipulating, aligning and disposing end turn phase insulators on a stator core.
Yet still another object is to develop new and improved methods utilizing end turn phase insulator characteristics to dispose the end turn insulators on a stator core.